The
Runnable
interface should be implemented by any
class whose instances are intended to be executed by a thread. The
class must define a method of no arguments called
run
.
This interface is designed to provide a common protocol for objects that
wish to execute code while they are active. For example,
Runnable
is implemented by class Thread
.
Being active simply means that a thread has been started and has not
yet been stopped.
In addition, Runnable
provides the means for a class to be
active while not subclassing Thread
. A class that implements
Runnable
can run without subclassing Thread
by instantiating a Thread
instance and passing itself in
as the target. In most cases, the Runnable
interface should
be used if you are only planning to override the run()
method and no other Thread
methods.
This is important because classes should not be subclassed
unless the programmer intends on modifying or enhancing the fundamental
behavior of the class.